Electrochromic display device and electrodeposition-type display device

ABSTRACT

Between each transparent pixel electrode driven by TFT as a drive device and a common electrode, a polymer layer located in contact with the transparent pixel electrode and electrically active to change in color by electrochemical oxidization or reduction and a polymeric solid electrolytic layer located in contact with the polymer layer and containing a coloring agent are interposed. since electrochemical oxidization or reduction brings about a color change, the contrast and the black concentration can be enhanced, and bronzing after long-time use does not occur.

TECHNICAL FIELD

This invention relates to an electrochromic display device and anelectrodeposition-type display device using a material variable in colorby electrochemical oxidation and reduction as the display material, andalso relates to a display apparatus using them.

BACKGROUND OF THE INVENTION

Along with recent dissemination of networks, documents having heretoforedistributed in form of printed matters have come to be distributed inform of so-called electronic documents. Additionally, more and morebooks and magazines are also becoming delivered in form of so-calledelectronic publications.

Conventional way of accessing to these kinds of information is to readfrom CRT or liquid crystal displays of computers. However, it is pointedout that emission-type displays cause much fatigue due to ergonomicreasons, and users cannot withstand long-time reading. Additionally,there is the disadvantage that a user can read it only at the placewhere a computer is set.

Together with recent distribution of note-type computers, there aredevices usable as portable displays. However, also these devices cannotbe used for reading over several hours or more because of the problem ofpower consumption in addition to the reason that the display is of anemission type. Reflection-type liquid crystal displays have also beendeveloped recently, and it will be possible to drive them with lowpower. However, reflectance of liquid crystal under no display(black-and-white display) is 30%, and visibility of such displays ismuch worse than prints on paper. Therefore, users are liable to fatigueand cannot withstand long-time reading.

To deal with these problems, devices called paper-like displays orelectronic paper are under development. They color their representationsmainly by moving color particles between electrodes by electrophoresisor by rotating dichromatic particles in an electric field. Thesemethods, however, involve the problems that gaps among particles absorblight and thereby degrade the contrast, and a writing speed acceptablefor practical use (within one second) cannot be attained unless raisingthe drive voltage to 100 V or more.

Electrochromic display apparatuses (ECD) generating color byelectrochemical operations are superior to the electrophoretic schemesfrom the viewpoint of high contrast, and have already been used inpractical light control glass and watch or clock displays. However,since light control glass and clock or watch displays do not originallyneed the matrix drive, they are not applicable to the use of displaysuch as electronic paper. Additionally, quality level of black is bad,in general, and their reflectance is still low.

Displays such as electronic paper are inevitably exposed continuously tolight such as sunlight or room light because of their purposes of use.In electrochromic display apparatuses of the type practically used aslight control glass and clock displays, certain organic materials areused for forming black portions. Generally, however, organic materialsexhibits poor light resistance, and are bronzed and degraded in blackoptical density after long use. Additionally, a matrix-driven displayapparatus taught by Japanese Patent Publication No. hei 4-73764 is alsoknown. However, the drive device merely composes a part of the liquidcrystal display apparatus.

In view of these technical problems, it is an object of the invention toprovide an electrochromic display device and an electrochromic displayapparatus operative by matrix driving and capable of enhancing thecontrast and the black optical density.

A further object of the invention is to provide an electrochromicdisplay device and an electrochromic display apparatus capable ofmaintaining the black optical density high without the problem ofbronzing even after long-time use.

SUMMARY OF INVENTION

To overcome the above-discussed problems, an electrochromic displaydevice according to the invention comprises: a first transparentelectrode controlled by a drive device: a polymer material layer locatedin contact with the transparent electrode and electrically active to bechangeable in color by electrochemical oxidation or reduction; apolymeric solid electrolytic layer located in contact with the polymermaterial layer and containing a coloring agent; and a second electrodelocated to interpose the polymer material layer and the polymeric solidelectrolytic layer between the first transparent electrode and thesecond electrode.

In the electrochromic display device having the above-summarizedconfiguration, when electricity is supplied between the firsttransparent electrode and the second electrode, the polymeric materiallayer interposed between the first transparent electrode and the secondelectrode is electrically activated to change in color. Since thepolymeric solid electrolytic layer adjacent to the polymeric materiallayer contains a coloring agent, the contrast upon a change in color inthe polymeric material layer can be enhanced. Since the firsttransparent electrode is controlled by the drive device, matrix drive ispossible when a plurality of drive devices are arranged.

An electrodeposition type display device according to the inventioncomprises: a first transparent electrode controlled by a drive device; apolymeric solid electrolytic layer containing a coloring agent and metalions; and a second electrode located to interpose the polymeric solidelectrolytic layer between the first transparent electrode and thesecond electrode.

In the electrodeposition type display device having the above-summarizedconfiguration, when electricity is supplied between the firsttransparent electrode and the second electrode, electrochemicaldeposition by gold ions contained in the polymeric solid electrolyticlayer occurs in the polymeric solid electrolytic layer, and a change incolor occurs. Since the polymeric solid electrolytic layer contains acoloring agent, the contrast upon a change in color in the polymericmaterial layer can be enhanced, and matrix drive is possible by usingthe drive device.

When a plurality of electrochromic display elements each having thestructure of the electrochromic display device according to theinvention or a plurality of electrodeposition type display elements eachhaving the structure of electrodeposition type display device accordingto the invention are arranged in form of a sheet, an electrochromicdisplay apparatus or electrodeposition type display apparatus is formed.

A method of manufacturing an electrochromic display apparatus or anelectrodeposition type display apparatus according to the inventioncomprises: the step of forming transparent pixel electrodes and drivedevices on a transparent support structure; the step of forming apolymer material layer electrically active and changeable in color byelectrochemical oxidization or reduction, and a polymeric solidelectrolytic layer containing a coloring agent on the transparentsupport structure having formed the transparent pixel electrodes and thedrive devices, or the step of forming a polymeric solid electrolyticlayer containing metal ions and a coloring agent; and the step offorming a common electrode opposed to the transparent pixel electrodes.

Following to the above-summarized manufacturing method, it is possibleto manufacture the electrochromic display apparatus or electrodepositiontype display apparatus including a plurality of electrodeposition typedisplay elements each having the structure of electrodeposition typedisplay device or a plurality of-electrodeposition type display elementseach having the structure of electrodeposition type display device thatare arranged in form of a sheet.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows fragmentary, perspective views of an electrochromic displayapparatus according to the first embodiment of the invention;

FIG. 2 is a cross-sectional view of the electrochromic display apparatusaccording to the first embodiment of the invention;

FIG. 3 shows fragmentary, perspective views of an electrodeposition typedisplay apparatus according to the second embodiment of the invention;

FIG. 4 shows cross-sectional views of the electrodeposition type displayapparatus according to the second embodiment of the invention;

FIGS. 5A, 5B and 5C are cross-sectional views showing respective stepsof a manufacturing method of an electrochromic display apparatusaccording to the third embodiment of the invention, in which FIG. 5A isa cross-sectional view after progress up to the step of forming TFT andtransparent pixel electrodes, FIG. 5B is a cross-sectional view afterprogress up to the step of immersion into an electrodeposition vessel,and FIG. 5C is a cross-sectional view after progress up to the step offorming a polymeric solid electrolytic layer;

FIGS. 6A, 6B and 6C are cross-sectional views showing respective stepscontinuous from the steps of FIGS. 5A, 5B and 5C of the manufacturingmethod of an electrochromic display apparatus according to the thirdembodiment of the invention, in which FIG. 6A is a cross-sectional viewafter progress up to the step of press-fitting a support structure, FIG.6B is a cross-sectional view after progress up to the step of bonding,and FIG. 6C is a cross-sectional view after progress up to the step ofattaching a sealing material;

FIGS. 7A, 7B and 7C are cross-sectional views showing respective stepsof a manufacturing method of an electrochromic display apparatusaccording to the fourth embodiment of the invention, in which FIG. 7A isa cross-sectional view after progress up to the step of forming TFT andtransparent pixel electrodes, FIG. 7B is a cross-sectional view afterprogress up to the step of forming a polymeric solid electrolytic layer,and FIG. 7C is a cross-sectional view after progress up to the step ofimmersion into an electrodeposition vessel;

FIGS. 8A, 8B and 8C are cross-sectional views showing respective stepsof a manufacturing method of an electrodeposition type display apparatusaccording to the fifth embodiment of the invention, in which FIG. 8A isa cross-sectional view after progress up to the step of forming TFT andtransparent pixel electrodes, FIG. 8B is a cross-sectional view afterprogress up to the step of forming a polymeric solid electrolytic layer,and FIG. 8C is a cross-sectional view after progress up to the step ofpress-fitting a support structure;

FIGS. 9A and 9B are cross-sectional views showing respective stepscontinuous from the steps of FIGS. 8A, 8B and 8C of the manufacturingmethod of an electrodeposition type display apparatus according to thefifth embodiment of the invention, in which FIG. 9A is a cross-sectionalview after progress up to the bonding step, and FIG. 9B is across-sectional view after progress up to the step of attaching asealing material;

FIG. 10 is a plan view of the structure of one surface of anelectrochromic display apparatus or electrodeposition type displayapparatus according to the sixth embodiment of the invention on whichtransparent pixel electrodes appear;

FIG. 11 is a plan view of the structure of one surface of theelectrochromic display apparatus or electrodeposition type displayapparatus according to the sixth embodiment of the invention, on whichthe common electrode appears;

FIG. 12 is a circuit diagram of the electrochromic display apparatus orelectrodeposition type display apparatus according to the sixthembodiment of the invention; and

FIG. 13 is a graph of a result of measurement, which shows a relationbetween current density and optical density (color density) in anelectrodeposition type display apparatus according to the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Electrochromic display apparatuses according to some embodiments of theinvention will now be explained below with reference to the drawings.Any of the electrochromic display apparatuses according to theembodiments has a structure in which a plurality of electrochromicdisplay elements each having the structure of an electrochromic displaydevice are arranged in form of a sheet.

First Embodiment

As shown in FIGS. 1 and 2, the electrochromic display apparatusaccording to this embodiment is characterized in arranging a pluralityof electrochromic display devices in form of a sheet, eachelectrochromic display device including a transparent pixel electrode 12serving as a first transparent electrode controlled by TFT (Thin FilmTransistor) 13 as a drive device, a polymer layer 14 electrically activeand variable in color due to electrochemical oxidation or reduction, apolymeric solid electrolytic layer 15 in contact with the polymer layer14 and containing a coloring agent, and a common electrode 16 commonlyused by this and other pixels to function as a second electrode opposedto the first transparent electrode.

Each combination of the transparent pixel electrode 12 and TFT 13 formone pixel, and a number of pixels are arranged in a matrix pattern on atransparent support structure 11. As the transparent support structure11, a transparent glass substrate such as quartz glass plate orwhiteboard glass plate, for example, may be used. In addition to these,other materials are also acceptable, namely, esters such as polyethylenenaphthalate and polyethylene terephthalate; cellulose esters such aspolyamide, polycarbonate and cellulose acetate; fluorine polymers suchas polyvinylidene fluoride,polytetrafluoroethylene-cohexafluoropropylene; polyethers such aspolyoxymethylene; polyolefins such as polyacetal, polystyrene,polyethylene, polypropylene and metylpentene polymer; and polyimide suchas polyimide-amide and polyetherimide. In case of using any of thesesynthetic resins, it may be formed into a rigid substrate not bendingeasily, or may be formed into a flexible film-like structure.

The transparent pixel electrode 12 is made of a transparent conductivefilm formed in a substantially rectangular or square pattern, and asshown in FIG. 1, individual pixels are isolated. Locally therein, TFT 13for each pixel is located. Here is preferably used an ITO film of amixture of In₂O₃ and SnO₂, or a film coated by SnO₂ or In₂O₃. It is alsoacceptable to dope Sn or Sb into the ITO film or the SnO₂— orIn₂O₃-coated film, and MgO or ZnO are also usable.

TFT 13 formed in each pixel is selected by a wiring not shown to controlthe associated transparent pixel electrode 12. TFT 13 is very efficientfor preventing cross-talk among pixels. TFT 13 is formed to occupy apart of the transparent pixel electrode, for example. Alternatively, thetransparent pixel electrode 12 may lie in a different level from TFT 13in the stacking direction. A gate line and a data line are connected toTFT 13, its gate electrode is connected to each gate line, one of thesource and the drain of TFT 13 is connected to a data line, and theother of the source and the drain is electrically connected to thetransparent pixel electrode 12. A drive device other than TFT 13 may bemade of a different material if it can be formed on a transparentsubstrate in a matrix drive circuit used in a flat type display.

The transparent pixel electrode 12 and TFT 13 are in contact with apolymer layer 14 that is a polymeric material layer. The polymer layer14 is made of a polymeric, electrochromic material that is electricallyactive. The polymer layer 14 is changed in color by electrochemicaloxidation or reduction, and when a potential difference is applied tothe transparent pixel electrode 12 as one of opposite electrodes of thecapacitance, it changes to black. The polymer layer 14 is preferablymade of a so-called conductive polymer obtained by electrolyticsynthesis. This is because the conductivity facilitates quick electronexchange interaction and ensures quick reaction of coloring anddecoloring. Examples of preferable polymers are shown in Table 1. Otherpolymer materials obtained by electrolytic oxidizing polymerization ofderivatives of pyrole, thiophene, azulene and aniline are also usable.It is also possible to use materials combining such materials with thepolymers shown in Table 1 and their derivatives.

TABLE 1 Oxidation Reduction potential (vs. potential (vs. CoulombPolymer Li⁺/Li) Li⁺/Li) efficiency Polypyrole 2.85 2.6 99% or morePolyaniline 4.2 4.0 99% or more Polyazulene 3.6 3.2 99% or morePolythiophene 4.5 3.6 96% Polyindole 3.8 3.5 95% Polycarbazole 3.7 3.681%

One of especially preferable materials among polymer materials shown inthe table (polypyrole, polyaniline, polyazulene, polythiophene,polyindole and polycarbazole) is polypyrole. Its reasons are 1) lowoxidation potential, 2) high coulomb efficiency, 3) black coloring uponoxidation and 4) long repetition lifetime, among others. The reason whymaterials of low oxidation potentials are preferred lies in that thosematerials lower in oxidation potential are stable in a colored state.The reason why materials having high coulomb efficiency are considereddesirable lies in that the high coulomb efficiency demonstratessuppression of side reaction as much. When the coulomb efficiency isnearly 100%, it demonstrates that almost no side reaction occurs andresults in lower lifetime as a device. It is an important nature as adocument display that the coloring upon oxidation is black. Polypyroleis black upon complete oxidation while the other materials are green orreddish black. Therefore, by employing polypyrole, it is possible toenhance the black concentration and improve the contrast. Additionally,the long repetition lifetime is another useful nature of polypyrole.

A polymeric solid electrolytic layer 15 is formed in contact with thecoloring polymer 14. If the polymeric solid electrolyte forming thepolymeric solid electrolytic layer 15 and the polymer material as theelectrochromic material are compounded, it is advantageous to alleviatefalling or powdering of the polymer material from the electrode due tovolume changes caused by coloring and decoloring and thereby increasethe durability.

As the matrix polymer used in the polymeric solid electrolyte formingthe polymeric solid electrolytic layer 15, examples of usable materialsare polyethylene oxide, polypropylene oxide, polyethylene imine andpolystyrene sulfide whose framework structure units are expressed by—(C—C—O)_(n)—, —(C—C(CH₃)—O)_(n)—, —(C—C—N)_(n)— or —(C—C—S)_(n)—.Branches may be added to any of these materials forming the main chainstructure. Polymethylmethacrylate, polyvinylidene fluoride,polyvinylidene chloride and polycarbonate are also preferable.

When the polymeric solid electrolytic layer 15 is formed, a quantity ofplasticizer is preferably added to the matrix polymer. Examples ofpreferable plasticizers are water, ethyl alcohol, isopropyl alcohol andtheir mixture, for example when the matrix polymer is hydrophilic. Ifthe matrix polymer is hydrophobic, propylene carbonate, dimethylcarbonate, ethylene carbonate, γ-butylolactone, acetonitrile, sulfolane,dimethoxyethane, ethyl alcohol, isopropyl alcohol, dimethylformamide,dimethylsulfoxide, dimethylacetamide, n-methylpyrolidone and theirmixtures.

The polymeric solid electrolyte is formed by melting an electrolyticsubstance into the matrix polymer, examples of usable materials as theelectrolyte are lithium salt such as LiCl, LiBr, LiI, LiBF₄, LiClO₄,LiPF₆ or LiCF₃SO₃, potassium salt such as KCl, KI or KBr, sodium saltsuch as NaCl, NaI, NaBr or tetra alkyl ammonium salt such as tetraethylene ammonium, boron tetra ethylene ammonium fluoride, tetraethylene ammonium perchlorate, boron tetrabuthylene ammonium fluoride,tetrabuthyl ammonium perchlorate or tetrabuthyl ammonium halide. Alkylchains of the above-mentioned 4-ammonium salt may be irregular.

If the polymeric solid electrolyte and the polymer material as theelectrochromic material are compounded, it is advantageous to alleviatefalling or powdering of the polymer material from the electrode due tovolume changes caused by coloring and decoloring and thereby increasethe durability. The polymeric solid electrolyte is obtained by firstforming the polymeric solid electrolytic material on the first electrodebeforehand by an appropriate-method, and thereafter carrying outelectrolytic oxidizing polymerization in an electrodeposition vesselcontaining pyrole monomer.

The polymeric solid electrolytic layer 15 contains a coloring agent forenhancing the contrast. In case the coloring of the polymer layer 14 isblack as mentioned above, a white material having a high concealingproperty is used as the background color. As this kind of material,white coloring particles may be used, such as those of titanium dioxide,calcium carbonate, silica, magnesium oxide, or aluminum oxide.

Mixture ratio of the coloring agent is preferably in the range ofapproximately 1 through 20 wt %, more preferably in the range ofapproximately 1 through 10 wt % and still more preferably in the rangeof approximately 5 to 10 wt % when inorganic particles are used.Inorganic white particles of titanium oxide, for example, do not solveinto polymers but merely disperse. Then, if the mixture ratio increases,inorganic particles aggregate, and it results in uneven optical density.Additionally, since those inorganic particles have no ion conductivity,an increase of the mixture ratio invites a decrease of the conductivityof the polymeric solid electrolyte. Taking both into consideration, theupper limit of the mixture ratio is approximately 20 wt %.

In case that inorganic particles are mixed as the coloring agent,thickness of the polymeric solid electrolytic layer 15 is adjustedpreferably in the range of 20 to 200 μm, more preferably in the range of50 to 150 μm and still more preferably in the range of 70 to 150 μm. Thepolymeric solid electrolytic layer 15 had better be thin because theresistance between electrodes decreases, and it contributes to adecrease of the coloring/decoloring time and power consumption. However,thinning the layer to 20 μm or less is not recommended because themechanical strength decreases to a level causing pin holes and cracking.In addition, if the layer is excessively thin, quantity of whiteparticles mixed inevitably decreases, and the white level (opticaldensity) is not sufficient.

The mixture ratio of the coloring agent may be 10 wt % when a pigment isused because coloring efficiency of a pigment is much higher than thatof inorganic particles. Therefore, any electrochemically stable pigmentcan make a contrast even when its quantity is small. Usually, anoil-soluble dye is preferable as the pigment.

On one side opposed to the first transparent electrode, a commonelectrode 16 is formed as the second electrode. The common electrode maybe made of any electrochemically stable material. Preferable materialsare platinum, chromium, aluminum, cobalt, palladium, and so on. Thecommon electrode can be made by forming a film of a conductor such as ametal film on a support structure 17. If a metal used for main reactioncan be supplied beforehand or any time thereafter, carbon can be used asthe common electrode. To support carbon on the electrode, there is themethod of preparing carbon ink by using a resin, and then print it onthe substrate surface. The use of carbon contributes to lowering thecost of the electrode.

The support structure 17 need not be transparent. It can be used asubstrate or film which can reliably hold the common electrode 16 andthe polymeric solid electrolytic layer 15. Some examples are glassplates such as quartz glass plate and whiteboard glass plates, ceramicsubstrates, paper substrates and wood substrates. In addition to these,other materials are also usable as synthetic resin substrates, namely,esters such as polyethylene naphthalate and polyethylene terephthalate;cellulose esters such as polyamide, polycarbonate and cellulose acetate;fluorine polymers such as polyvinylidene fluoride,polytetrafluoroethylene-cohexafluoropropylene; polyethers such aspolyoxymethylene; polyolefins such as polyacetal, polystyrene,polyethylene, polypropylene and metylpentene polymer; and polyimide suchas polyimide-amide and polyetherimide. In case of using any of thesesynthetic resins, it may be formed into a rigid substrate not bendingeasily, or may be formed into a flexible film-like structure. If thecommon electrode 16 is sufficiently rigid, the support structure 17 maybe omitted.

As shown in FIG. 2, for the purpose of placing the first transparentelectrode and the second electrode face-to-face, a sealing resin portion18 is formed along the perimeter to hold both support structures 11, 17.The sealing resin portion 18 will reliably hold these support structures11, 17, and other intervening components, namely, transparent pixelelectrode 12, TFT 13, polymer layer 14, polymeric solid electrolyticlayer 15 and common electrode 16.

Using the above-explained structure, the electrochromic displayapparatus according to the embodiment is capable of matrix driving byusing TFT 13, and can enhance the contrast and the black optical densityby selecting an appropriate material of the polymer layer 14.

Second Embodiment

As shown in FIGS. 3 and 4, an electrodeposition type display apparatusaccording to this embodiment is characterized in arranging a pluralityof electrodeposition type display devices in form of a sheet, which eachelectrodeposition type display device includes a transparent pixelelectrode 22 serving as the first transparent electrode controlled byTFT (Thin Film Transistor) 23 as a drive device; a polymeric solidelectrolytic layer 25 containing metal ions and a coloring agent, and acommon electrode 26 commonly used by this and other pixels to functionas the second electrode opposed to the first transparent electrode.

In the electrodeposition type display apparatus according to theembodiment, each combination of the transparent pixel electrode 22 andTFT 23 form one pixel, and a number of pixels are arranged in a matrixpattern on a transparent support structure 21. As the transparentsupport structure 11, a transparent glass substrate such as quartz glassplate or whiteboard glass plate, for example, may be used similarly tothe first embodiment. In addition to these, other materials are alsoacceptable, namely, esters such as polyethylene naphthalate andpolyethylene terephthalate; cellulose esters such as polyamide,polycarbonate and cellulose acetate; fluorine polymers such aspolyvinylidene fluoride, polytetrafluoroethylene-cohexafluoropropylene;polyethers such as polyoxymethylene; polyolefins such as polyacetal,polystyrene, polyethylene, polypropylene and metylpentene polymer; andpolyimide such as polyimide-amide and polyetherimide. In case of usingany of these synthetic resins, it may be formed into a rigid substratenot bending easily, or may be formed into a flexible film-likestructure.

The transparent pixel electrode 22 is made of a transparent conductivefilm formed in a substantially rectangular-or square pattern, and asshown in FIG. 3, individual pixels are isolated. Locally therein, TFT 23for each pixel is located. Here is preferably used an ITO film of amixture of In₂O₃ and SnO₂, or a film coated by SnO₂ or In₂O₃. It is alsoacceptable to dope Sn or Sb into the ITO film or the SnO₂— orIn₂O₃-coated film, and MgO or ZnO are also usable.

TFT 23 formed in each pixel is selected by a wiring not shown to controlthe associated transparent pixel electrode 22. TFT 23 is very efficientfor preventing cross-talk among pixels. TFT 23 is formed to occupy apart of the transparent pixel electrode, for example. Alternatively, thetransparent pixel electrode 22 may lie in a different level from TFT 23in the stacking direction. A gate line and a data line are connected toTFT 23, its gate electrode is connected to each gate line, one of thesource and the drain of TFT 13 is connected to a data line, and theother of the source and the drain is electrically connected to thetransparent pixel electrode 22. A drive device other than TFT 23 may bemade of a different material if it can be formed on a transparentsubstrate in a matrix drive circuit used in a flat type display.

In the electrodeposition type display apparatus according to the instantembodiment, the polymeric solid electrolytic layer 25 contains metalions used for changing the color. The metal ions used for color changeelectrochemically deposit as so-called electrolytic plating, andreciprocally elute as the opposite reaction to effectuate display. Metalions capable of coloring and decoloring by electrochemical depositionand elution are not limited to specific kinds of metals. However, someexamples of such metal ions are bismuth, copper, silver, lithium, iron,chromium, nickel and cadmium ions and their combinations. Especiallypreferable metal ions are bismuth and silver ions because reciprocalreaction can be easily brought about and the color changing degree upondeposition is high.

As the matrix polymer used in the polymeric solid electrolyte formingthe polymeric solid electrolytic layer 25 containing metal ions,examples of usable materials are polyethylene oxide, polypropyleneoxide, polyethylene imine and polystyrene sulfide whose frameworkstructure units are expressed by —(C—C—O)_(n)—, —(C—C(CH₃)—O)_(n)—,—(C—C—N)_(n)— or —(C—C—S)_(n)—. Branches may be added to any of thesematerials forming the main chain structure. Polymethylmethacrylate,polyvinylidene fluoride, polyvinylidene chloride and polycarbonate arealso preferable.

When the polymeric solid electrolytic layer 25 is formed, a quantity ofplasticizer is preferably added to the matrix polymer. Examples ofpreferable plasticizers are water, ethyl alcohol, isopropyl alcohol andtheir mixture, for example when the matrix polymer is hydrophilic. Ifthe matrix polymer is hydrophobic, propylene carbonate, dimethylcarbonate, ethylene carbonate, γ-butylolactone, acetonitrile, sulfolane,dimethoxyethane, ethyl alcohol, isopropyl alcohol, dimethylformamide,dimethylsulfoxide, dimethylacetamide, n-methylpyrolidone and theirmixtures.

The polymeric solid electrolyte is formed by melting an electrolyticsubstance into the matrix polymer, examples of usable materials as theelectrolyte are lithium salt such as LiCl, LiBr, LiI, LiBF₄, LiClO₄,LiPF₆ or LiCF₃SO₃, potassium salt such as KCl, KI or KBr, sodium saltsuch as NaCl, NaI, NaBr or tetra alkyl ammonium salt such as tetraethylene ammonium, boron tetra ethylene ammonium fluoride, tetraethylene ammonium perchlorate, boron tetrabuthylene ammonium fluoride,tetrabuthyl ammonium perchlorate or tetrabuthyl ammonium halide. Alkylchains of the above-mentioned 4-ammonium salt may be irregular.

The polymeric solid electrolytic layer 25 contains a coloring agent forenhancing the contrast. In case the coloring of the metal ions is blackas mentioned above, a white material having a high concealing propertyis used as the background color. As this kind of material, whitecoloring particles may be used, such as those of titanium dioxide,calcium carbonate, silica, magnesium oxide, or aluminum oxide. Further,a pigment for coloring can be used as well.

Mixture ratio of the coloring agent is preferably in the range ofapproximately 1 through 20 wt %, more preferably in the range ofapproximately 1 through 10 wt % and still more preferably in the rangeof approximately 5 to 10 wt % when inorganic particles are used. In casethat inorganic particles are mixed as the coloring agent, thickness ofthe polymeric solid electrolytic layer 25 is adjusted preferably in therange of 20 to 200 μm, more preferably in the range of 50 to 150 μm andstill more preferably in the range of 70 to 150 μm. Reasons of suchconditions are the same as those in the explanation of the fistembodiment. So explanation thereof is omitted here for avoidingredundancy.

The mixture ratio of the pigment-based coloring agent may be 10 wt %because coloring efficiency of a pigment is much higher than that ofinorganic particles. Therefore, any electrochemically stable pigment canmake a contrast even when its quantity is small. Usually, an oil-solubledye is preferable as the pigment.

On one side opposed to the first transparent electrode, a commonelectrode 26 is formed as the second electrode. The common electrode maybe made of any electrochemically stable material. Preferable materialsare platinum, chromium, aluminum, cobalt, palladium, and so on. Thecommon electrode can be made by forming a film of a conductor such as ametal film on a support structure 27. If a metal used for main reactioncan be supplied beforehand or any time thereafter, carbon can be used asthe common electrode. To support o carry carbon on the electrode, thereis the method of preparing carbon ink by using a resin, and then printit on the substrate surface. The use of carbon contributes to loweringthe cost of the electrode.

The support structure 27 need not be transparent. It can be used asubstrate or film which can reliably hold the common electrode 26 andthe polymeric solid electrolytic layer 25. Its candidate materials arethe same as those of support structure according to the firstembodiment. Additionally, as shown in FIG. 4, for the purpose of placingthe first transparent electrode and the second electrode face-to-face, asealing resin portion 28 is formed along the perimeter to hold bothsupport structures 11, 17. The sealing resin portion 28 will reliablyhold these support structures 21, 27, and other intervening components,namely, transparent pixel electrode 22, TFT 23, polymer layer 24,polymeric solid electrolytic layer 25 and common electrode 26.

Using the above-explained structure, the electrodeposition type displayapparatus according to the embodiment is capable of matrix driving byusing TFT 23, and can enhance the contrast and the black optical densityby making use of metal ions contained in the polymeric solidelectrolytic layer 25.

Third Embodiment

This embodiment is directed to a method of manufacturing theelectrochromic display apparatus according to the first embodiment. Themethod will be explained below in the order of its steps with referenceto FIGS. 5A through 5C and FIGS. 6A through 6C.

First referring to FIG. 5A, transparent pixel electrodes in form of anITO film and thin-film transistors 33 are formed on a transparentsupport structure 31 such as a glass substrate for each pixel. Thethin-film transistor 33 is formed by using a known semiconductormanufacturing technique, and the ITO film is formed by a technique suchas vapor deposition or sputtering, for example. A transparent pixelelectrode 32 and a thin-film transistor 33 are formed for each pixel,and a number of pixels are arranged in an matrix array on thetransparent support structure 31.

After the transparent pixel electrodes 32 and the thin-film transistors33 are formed on the transparent support structure 31, a lead portionconnectable to a drive circuit 34 is formed. Then the entirety isimmersed into electrodeposition liquid 36 in an electrodeposition vessel35. The electrodeposition liquid 36 functions to electrolyticallydeposit a polymer layer of polypyrole, for example. The drive circuit 34supplies electricity to each transparent pixel electrode 32 toelectrolytically deposit the polymer layer, not shown, of polypyrole,for example, on each transparent pixel electrode 32. In this process,the transparent pixel electrodes 32 face to an electrodepositionelectrode 37 via the electrodeposition liquid 36. Subsequently, theentirety is again immersed into the electrodeposition liquid in theelectrodeposition vessel not containing a color-changing polymermaterial (in this case, pyrole) to once return the tops of thetransparent pixel electrodes to transparency by deionizing the polymerlayer. Thereafter, the transparent support structure 31 is removed fromthe electrodeposition liquid, washed with ethanol, and dried by vacuumdrying.

After that, as shown in FIG. 5C, a polymeric solid electrolytic layer 38is formed on the transparent support structure 31. First, a syntheticresin as the matrix polymer of the polymeric solid electrolytic layer 38and a material forming the electrolyte such as lithium salt, potassiumsalt, sodium salt, or tetra alkyl ammonium salt are mixed, and whiteparticles are additionally dispersed as a coloring agent to prepare thematerial. This polymeric solid electrolytic material is coated to formthe polymeric solid electrolytic layer 38.

In parallel therewith, a common electrode 39 in form of a palladium filmof an appropriate thickness is formed on the support structure 40 inform of a polyethylene terephthalate. The common electrode 39 on thesupport structure 40 is press-fit to the polymeric solid electrolyticlayer 38 not yet cured as shown in FIG. 6A, and they are bonded togetheras shown in FIG. 6B. After the bonding, a polymeric solid electrolyticlayer gelled by vacuum drying is formed between the support structure 40and the transparent support structure 31. Then, as shown in FIG. 6C, aseal member 41 is attached to the end of the bonding to complete theelectrochromic display apparatus.

In this embodiment, since the electrically active polymer layer isdeposited by immersion into the electrodeposition liquid 36 in theelectrodeposition vessel 35 and a supply of electricity, the polymerlayer is formed on the transparent electrodes to be compoundedtherewith. Therefore, the polymer layer is prevented from falling orother undesirable events, and can be formed concentrically on thetransparent pixel electrodes 32.

Fourth Embodiment

This embodiment is directed to another method of manufacturing theelectrochromic display apparatus according to the first embodiment,which is a modification from the third embodiment. This embodiment willbe explained below in order of its steps with reference to FIGS. 7Athrough 7C.

Similarly to the manufacturing method of the third embodiment, firstreferring to FIG. 7A, transparent pixel electrodes in form of an ITOfilm and thin-film transistors 33 are formed on a transparent supportstructure 31 such as a glass substrate for each pixel. The thin-filmtransistor 33 is formed by using a known semiconductor manufacturingtechnique, and the ITO film is formed by a technique such as vapordeposition or sputtering, for example. A transparent pixel electrode 32and a thin-film transistor 33 are formed for each pixel, and a number ofpixels are arranged in an matrix array on the transparent supportstructure 31. A lead portion (not shown) connectable to the drivecircuit in a later step is also formed.

After that, as shown in FIG. 7B, a polymeric solid electrolytic layer 38is formed on the transparent support structure 31. First, a syntheticresin as the matrix polymer of the polymeric solid electrolytic layer 38and a material forming the electrolyte such as lithium salt, potassiumsalt, sodium salt, or tetra alkyl ammonium salt are mixed, and whiteparticles are additionally dispersed as a coloring agent to prepare thematerial. This polymeric solid electrolytic material is coated to formthe polymeric solid electrolytic layer 38. At this stage, the polymericsolid electrolytic layer 38 is dried and gelled.

After the polymeric solid electrolytic layer 38 on the transparentsupport structure 31 is dried and gelled, the entirety is immersed intoelectrodeposition liquid 36 in an electrodeposition vessel 35 as shownin FIG. 7C. The electrodeposition liquid 36 functions toelectrolytically deposit a polymer layer of polypyrole, for example. Thedrive circuit 34 supplies electricity to each transparent pixelelectrode 32 to electrolytically deposit the polymer layer, not shown,of polypyrole, for example, on each transparent pixel electrode 32. Inthis process, the transparent pixel electrodes 32 face to anelectrodeposition electrode 37 via the electrodeposition liquid 36.Immediately after the electrodeposition, the support structure as thesecond electrode and the surface with the common electrode are bonded,and through the steps shown in FIGS. 6A through 6C, the elctrochromicdisplay apparatus is completed.

Fifth Embodiment

This embodiment is directed to a method of manufacturing theelectrodeposition type display apparatus according to the secondembodiment. The method will be explained below in the order of its stepswith reference to FIGS. 8A through 8C, FIGS. 9A and 9B.

First referring to FIG. 8A, transparent pixel electrodes in form of anITO film and thin-film transistors 53 are formed on a transparentsupport structure 51 such as a glass substrate for each pixel. Thethin-film transistor 53 is formed by using a known semiconductormanufacturing technique, and the ITO film is formed by a technique suchas vapor deposition or sputtering, for example. A transparent pixelelectrode 52 and a thin-film transistor 53 are formed for each pixel,and a number of pixels are arranged in an matrix array on thetransparent support structure 51.

After the transparent pixel electrodes 52 and the thin-film transistors53 are formed on the transparent support structure 51, a polymeric solidelectrolytic layer 54 is formed on the transparent support structure 51as shown in FIG. 8B. In the process of forming the polymeric solidelectrolytic layer 54, a synthetic resin as the matrix polymer of thepolymeric solid electrolytic layer 54, a material forming theelectrolyte such as lithium salt, potassium salt, sodium salt, or tetraalkyl ammonium salt, and a metal ion generating agent such as bismuthchloride are mixed altogether, and white particles are additionallydispersed as a coloring agent to prepare the material. This polymericsolid electrolytic material is coated to form the polymeric solidelectrolytic layer 54.

In parallel therewith, as shown in FIG. 8C, a common electrode 55 inform of a palladium film of an appropriate thickness is formed on thesupport structure 56 in form of a polyethylene terephthalate. The commonelectrode 55 on the support structure 56 is press-fit to the polymericsolid electrolytic layer 54 not yet cured, and they are bonded togetheras shown in FIG. 9A. After the bonding, a polymeric solid electrolyticlayer gelled by vacuum drying is formed between the support structure 56and the transparent support structure 51. Then, as shown in FIG. 9B, aseal member 57 is attached to the end of the bonding to complete theelectrodeposition type display apparatus.

In this embodiment, metal ions are introduced together with theelectrolyte at the step of preparation of the polymeric solidelectrolytic layer 54. Therefore, the polymeric solid electrolytic layer54 and the color-variable material are combined in a relatively easyprocess, and the manufacturing process is simplified accordingly.

Sixth Embodiment

The electrochromic display apparatus or electrodeposition type displayapparatus according to the embodiment is an example in which potentialdetector electrodes 64, 65 are formed as third electrodes independentlyfrom the first transparent electrode and the second electrode (commonelectrode). These potential detector electrodes 64, 65 are placed aselectrically insulated members on a common plane of the transparentsupport structure together with the transparent pixel electrodes orcommon electrode, and they are used for detecting the potential of thetransparent pixel electrodes or common electrode on the transparentsupport structure.

FIG. 10 is a plan view of one surface on which the transparent pixelelectrodes appear. On a transparent support structure 61, a transparentpixel electrode 63 and a TFT 62 as a drive device are formed for eachpixel, and a number of pixels are arranged in a matrix array. Thepotential detector electrode 64 for detecting the potential oftransparent pixel electrodes is formed in space among pixels to extendin a cross-like pattern, and its end portions (shown by black dots) aresilver or aluminum electrodes having a thickness around 1000 nm. Theline portions connecting the end portions are silver or aluminum linearwiring portions having a width around 1 μm. Since this potentialdetector electrode 64 is a electrically insulated member formed on acommon plane together with the transparent pixel electrodes 63, it canprecisely monitor the potential of the transparent pixel electrodes 63,and thereby precisely detect reaction occurring in the transparent pixelelectrodes 63. As the material of the potential detector electrode 64, astable metal material free from spontaneous elution into mediumsabsolutely irrelevant to reaction is preferably selected. For example,platinum, chromium, aluminum, cobalt, palladium or silver can beselected similarly to the second electrode.

FIG. 11 is a plan view of one surface on which the common electrodeappears. A common electrode is formed on the support structure 66, and apotential detector electrode 65 is also formed in a pattern similar tothe inverted π. Since this potential detector electrode 65 is aelectrically insulated member formed on a common plane together with thecommon electrode 67, it can precisely monitor the potential of thecommon electrode 67, and thereby precisely detect reaction occurring inthe common electrodes 67. As the material of the potential detectorelectrode 65, a stable metal material free from spontaneous elution intomediums absolutely irrelevant to reaction is preferably selected. Forexample, platinum, chromium, aluminum, cobalt, palladium or silver canbe selected similarly to the second electrode. Since the potentialdetector electrode 65 can be made of the same material as that of thecommon electrode on the common plane, it can be easily formed bypatterning the space-between the potential detector electrode 65 and thecommon electrode 67.

FIG. 12 is a circuit diagram of the electrochromic display apparatus orelectrodeposition type display apparatus having a potential detectorelectrode 76. A number of pixels each composed of TFT 74 and atransparent pixel electrode 75 are arranged in a matrix array, and oneof opposite electrodes of the capacitance serves as a common electrode.Data line drive circuits 72, 72a and a gate line drive circuit forselecting respective pixels are provided, and a predetermined data line78 and a gate line 77 are selected by a signal from a signal controller71. The potential detector electrode 76 is configured to connect fromthe signal controller 71, and the potential of the pixel portion can bemonitored with the supply of a signal from the potential detectorelectrode 76. That is, a stable metal material free from spontaneouselution into mediums absolutely irrelevant to reaction is selected asthe material of the potential detector electrode 76, and the electrode76 can precisely monitor the progress of main reaction of electrochromicor metal precipitation dissolution. At the time when sufficientdeposition or electrochemical reaction is confirmed through the monitorusing the potential detector electrode 76, further reaction can bestopped.

Some examples will be explained together with their manufacturingmethods. Although various effects of the invention are explained by wayof these examples, the invention is not limited to them.

EXAMPLE 1

(Fabrication of Display Electrode)

A two-dimensional arrangement of ITO films and TFT (thin filmtransistor) aligned by 150 μm pitch were formed on a 1.5 mm thick glasssubstrate sized 10×10 cm. After a lead portion to be connected to thedrive circuit from the substrate was formed by a known technique, andthe entirety was next set in an electrodeposition vessel (see FIG. 5B).The electrodeposition liquid was prepared by solving 1M of tetraethylammonium tetrafluoroborate and 0.1M of pyrole in propylene carbonate.After that, 0.2 μA current was supplied to respective pixels from thedrive circuit until the supplied electricity reached 20 μC. As a result,black polypyrole deposited on each ITO.

Subsequently, the glass substrate was set in the electrodepositionvessel containing the electrodeposition liquid obtained by solving 1M oftetraethyl ammonium tetrafluoroborate in propylene carbonate, voltage ofeach pixel electrode is adjusted to 1V relative to an Ag⁺/Ag referenceelectrode, and polypyrole having doped upon electrolytic polymerizationwas deionized. Polypyrole was changed to yellowish transparency.Subsequently, after the substrate was taken out and washed with ethanol,it was dried by vacuum drying.

(Adjustment and Coating of Polymeric Solid Electrolyte)

1 weight part of polyvinylidene fluoride of molecular weight 350,000approximately was mixed in 10 weight part of 1:1 mixture solvent ofpropylene carbonate and ethylene carbonate containing 1.7 weight part ofboron tetrabuthyl ammonium fluoride, and the mixture was heated to 120°C. to prepare a homogenous solution. Subsequently, 0.2 weight part oftitanium dioxide having the mean grain size 0.5 μm was added to thesolution, and uniformly dispersed by homogenizer. This was next coatedon the glass substrate with a doctor blade up to the thickness 60 μm,then the common electrode as the second electrode, explained later, wasimmediately bonded, and dries by vacuum drying under 110° C. and 0.1 Mpafor one hour. Thus the gelled polymeric solid electrolyte was formedbetween two electrodes. The end surfaces with the bonding seam weresealed with an adhesive.

(Second Electrode (Counter Electrode, Common Electrode))

A 3000 Å palladium film was formed on a 0.5 mm thick polyethyleneterephthalate film sized 10×10 cm by sputtering. It was press-fitimmediately after being coated with the polymeric solid electrolyte.

(Drive and Estimation of Display Characteristics)

Using a known active matrix drive circuit, display electrodes wereoxidized with 5 μC electricity per pixel upon coloring, and reduced withthe same quantity of electricity upon decoloring to switch the blackdisplay and colorless (white) display. Reflectance of colorless displaywas 70%, and optical density (OD) of the display portion upon coloring(black) was approximately 1.3 (reflectance 5%). Therefore, reflectancecontrast of 1:12 was obtained. After the sample was maintained in thecoloring state, the circuit was opened, and the sample was left. Afterone week, optical density of the display portion was approximately 1.0,and the sample was confirmed to have a memory capability. The cycle ofcoloring and decoloring was repeated, and the number of repetitioncycles until the black concentration upon coloring degrades to 1.0 orlower was approximately eight million times.

EXAMPLE 2

Polymeric solid electrolyte was coated on a TFT substrate beforehand anddried and gelled similarly to Example 1. Thereafter, the substrate wasintroduced into the electrodeposition vessel, and electricity wassupplied similarly to Example 1. As a result, polypyrole deposited onITO electrodes in a compounded form with the matrix polymer of polymericsolid electrolyte. The substrate was removed from the electrodepositionvessel and immediately bonded to the counter electrode (secondelectrode), and the sample was dried under the same condition.

When the sample was driven and evaluated similarly to Example 1, therepetition number of cycles was approximately thirty million times, andthe other characteristics were equivalent.

EXAMPLE 3

(Fabrication of Display Electrodes, and Preparation and Coating ofPolymeric Solid Electrolyte)

A two-dimensional arrangement of ITO films and TFT (thin filmtransistor) aligned by 150 μm pitch were formed on a 1.5 mm thick glasssubstrate sized 10×10 cm. Thereafter, 1 weight part of polyvinylidenefluoride of molecular weight 350,000 approximately was mixed in 10weight part of 1:1 mixture solvent of water and isopropyl alcoholcontaining 1.7 weight part of lithium bromide and 1.7 weight part ofbismuth chloride, and the mixture was heated to 120° C. to prepare ahomogenous solution. Subsequently, 0.2 weight part of titanium dioxidehaving the mean grain size 0.5 μm was added to the solution, anduniformly dispersed by homogenizer. This was next coated on the glasssubstrate with a doctor blade up to the thickness 60 μm, then the commonelectrode as the second electrode, explained later, was immediatelybonded, and dries by vacuum drying under 110° C. and 0.1 Mpa for onehour. Thus the gelled polymeric solid electrolyte was formed between twoelectrodes. The end surfaces with the bonding seam were sealed with anadhesive.

(Second Electrode (Counter Electrode, Common Electrode))

A 3000 Å palladium film was formed on a 0.5 mm thick polyethyleneterephthalate film sized 10×10 cm by sputtering. It was press-fitimmediately after being coated with the polymeric solid electrolyte.

(Drive and Estimation of Display Characteristics)

Using a known active matrix drive circuit, display electrodes wereoxidized with 5 μC electricity per pixel upon coloring, and reduced withthe same quantity of electricity upon decoloring to switch the blackdisplay and colorless (white) display. Reflectance of colorless displaywas 70%, and optical density (OD) of the display portion upon coloring(black) was approximately 0.8 (reflectance 13%). Therefore, reflectancecontrast of 1:5 was obtained. After the sample was maintained in thecoloring state, the circuit was opened, and the sample was left. Afterone week, no substantial change in optical density of the display wasobserved, and the sample was confirmed to have a memory capability. Thecycle of coloring and decoloring was repeated, and the number ofrepetition cycles until the black concentration upon coloring degradesto 1.0 or lower was approximately eighty million times.

EXAMPLE 4

A sample was prepared using the same conditions that of Example 3,excepting the use of a mixture of polyvinylidene chloride fluoride,LiBF₄ and AgClO₄. When the sample was driven and evaluated similarly toExample 3, the repetition number of cycles was approximately thirtymillion times, and the other characteristics were equivalent.

EXAMPLE 5

Measurement was carried out in regard to relations between the quantityof electricity supplied to pixel electrodes in an electrodeposition typedisplay apparatus and coloring concentration (optical density) of thepixels by deposited silver. Results of the measurement are shown in FIG.13. To obtain well visible characters, in general, concentration of thecharacter portion should be at least 1.0 in optical density (OD), andpreferably at least 1.5. Therefore, it is appreciated from the resultsshown in FIG. 13 that the quantity of electricity required isapproximately not less than 5 mC/cm², and preferably not less than 10mC/cm². Quantity of electricity below that range will produce palecharacters difficult to read. Optical density beyond 1.5 will providesufficient visibility. However, even if it is raised than that value,visibility is not improved so much because of saturation for the humansense. Additionally, when optical density is raised beyond 1.5, since alarge quantity of metal such as silver deposits, opposite reaction(decoloring reaction) will become insufficient, and incompleteextinguishment will occur. Therefore, quantity of electricity suppliedis preferably adjusted to or below 20 mC/cm².

According to the above-explained structure, the electrochromic displaydevice and apparatus according to the invention are capable of matrixdriving by using drive devices formed in respective pixels, and canenhance the contrast and the black concentration by the use of a polymermaterial in contact with the polymeric solid electrolyte to colorelectrochemical oxidation and reduction.

The electrodeposition type display device and apparatus can remove theproblem of bronzing and keep the black concentration high even afterlong-use because of the use of polymeric solid electrolyte containingmetal ions.

The manufacturing method of an electrochromic display apparatus or anelectrodeposition type display apparatus according to the invention caneasily manufacture the electrochromic display apparatus orelectrodeposition type display apparatus having the above-explainedstructure.

1. An electrodeposition type display device comprising: a firsttransparent electrode controlled by a drive device; a polymeric solidelectrolytic layer containing a coloring agent and metal ions; and asecond electrode located to interpose said polymeric solid electrolyticlayer between said first transparent electrode and said secondelectrode, wherein said polymeric solid electrolytic layer is alamination of a plurality of layers, and said coloring agent iscontained only in one or some of said layers.
 2. An electrodepositiontype display device comprising: a first transparent electrode controlledby a drive device; a polymeric solid electrolytic layer containing acoloring agent and metal ions; and a second electrode located tointerpose said polymeric solid electrolytic layer between said firsttransparent electrode and said second electrode, wherein a materiallayer capable of introducing and releasing ions or a material layercapable of producing an electrochemical oxidation-reduction reaction isplaced between said polymeric solid electrolytic layer and said secondelectrode.
 3. The electrodeposition type display device according toclaim 2 wherein said material layer contains carbon.
 4. Theelectrodeposition type display device according to claim 2 wherein saidpolymeric solid electrolytic layer contains a growth inhibitor forinhibiting deposition of said metal ions.
 5. The electrodeposition typedisplay device according to claim 4 wherein said growth inhibitor has agroup including an oxygen atom or a sulfur atom.